Httpd – Denying access to website via htaccess based on http header

Your rules indicate these procedures:

If the URL is only numbers, go to the beta URL followed by those numbers and stop.

If you visit domain1, go to the same URL at domain2 and stop.

When an L is encountered or the rules are finished, the processing ends. Anything else happening is a new connection from the browser. This is probably what is confusing for you—the order matters, then the matches. The L should take care of the problem you have when they're in order:

RewriteEngine on

RewriteRule ^([0-9]+)$ /beta/forward.php?id=$1 [L] # end of processing [L] if it's only numeric

RewriteCond %{HTTP_HOST} ^domain1\.net$ [NC] # if case-insensitive match of domain1.net…

RewriteRule ^(.*)$ http://domain2.net/$1 [R=301,L] # redirect to domain2.net. End [L]

Maybe you are thinking to complicated, just deny all access and then allow access to index.php and the folder itself. For example:

Order allow,deny
Deny from All

<FilesMatch "^(index\.php)?$">
        Allow from All
</FilesMatch>

If you don't even want http://doma.in/folder/ to work you can replace the FilesMatch directive with Files index.php. Keep in mind that it depends on your DirectoryIndex directive what file will be displayed when accessing a folder without filename.

Edit: To answer the question in your comment, I think you will need a more powerfull .htaccess using mod_rewrite. You can't use Directory and DirectoryMatch in a .htaccess file accordingly to the Apache documentation. Because the request is being denied before the RewriteRule can add a trailing slash you can't add the trailing slash with mod_write.

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !/index\.php$
    RewriteRule ^.*$ - [F]
</IfModule>

<IfModule !mod_rewrite.c>
    Order allow,deny
    Deny from All
</IfModule>